Pressure measuring devices such as sphygmomanometers, that are used to measure the arterial blood pressure of a patent, typically include a pneumatic bulb which inflates a pressure chamber of an attached sleeve that is fitted over a limb (i.e., an arm or a leg) of the patient. A diaphragm or bellows assembly, responsive to changes in fluid pressure of the pneumatic bulb and the sleeve pressure chamber, is positioned in a gage housing which is fluidly connected to the pressure chamber of the sleeve through flexible tubes or hoses. In a mechanical gage housing, a pointer of a dial indicator is interconnected to the bellows assembly through a movement mechanism that is retained within the gage housing, whereby inflation of the bellows causes corresponding circumferential movement of the pointer, enabling a blood pressure measurement procedure to be carried out by a caregiver.
Typically, the above referred to movement mechanisms are quite intricate and complex, and are akin in terms of their manufacture and precision to Swiss watches. For example, and in one such movement mechanism, a pair of diaphragm springs are attached adjacent opposing ends of a spindle. A bottom end of the spindle is placed in contact with the bellows assembly and a twisted bronze band perpendicularly disposed at the top end of the spindle is connected in parallel by a horizontally disposed spring bent part. As the spindle deflects axially in response to the inflation of the bellows, the bent spring part is also caused to deflect, thereby causing the band to twist. The pointer, attached to the bronze band, therefore is caused to rotate in relation to an adjacent dial face.
Devices, such as the foregoing, include numerous moving and relatively complex components, some or each of having numerous bearing surfaces. Therefore, such known devices must be manufactured with relatively strict tolerance margins and significant associated costs in terms of both precision and failure rate in order to minimize errors.
In addition, any adjustments required after assembly of the above mechanisms, such as to null the pointer or adjust the sensitivity of the device, require substantial tear down or at least some undesired disassembly.
Furthermore, discrete and separate elements are typically required within the instrument housing for independently supporting the movement mechanism and the bellows assembly, respectively, and for defining an expansion chamber for the bellows assembly there between.
A more recent and simplified movement mechanism is described in U.S. Pat. No. 5,996,829, incorporated by reference in its entirety. This mechanism includes a vertically disposed axial cartridge having a spirally wrapped ribbon spring with one end mounted to an axially movable elongate shaft and the remaining end of the spring being attached to a fixed tubular sleeve. A bottom portion of the elongate shaft is positioned relative to an expandable diaphragm or bellows, wherein subsequent axial translation of the shaft, caused by movement of the diaphragm, elongates the spirally wound ribbon spring and produces repeatable circumferential movement of a pointer supported at the top end of the shaft. The above movement mechanism is far smaller and more lightweight than those previously known due to its simplified construction.
A further advance, described in U.S. Pat. No. 6,168,566, also incorporated by reference in its entirety, permits the design of a housing retaining the movement mechanism described in the '829 patent to be even more compact.
One feature common to the above pressure measuring devices is the need to fluidly interconnect the gage housing containing the movement mechanism, the dial face and the indicating member with the interior of the inflatable sleeve. This interconnection is typically done using an elongated hose that is connected to a barb or coupling located on the sleeve exterior at one end of the hose and to an inlet port disposed on one end of the gage housing. It is a general object in the field to simplify the manufacture of these devices and to better integrate the design thereof.
More recently, electronic versions of pressure measuring devices have become much more prevalent and conspicuous in their use in the field. These devices such as those manufactured by Omron, Inc. among others can be mounted to the arm or wrist of a patient. These devices have a battery powered electronically based device that converts the output from the sleeve into a pressure reading output to the user. There is still reliance, however, upon inflation and deflation of an inflatable sleeve and more particularly, there is a fluid interconnection between the interior of the sleeve and the interior of the gage housing. In addition and to date, all of these devices have always been part of an integrated assembly, including the sleeve, whereby replacement has required replacement of not only the sleeve, but also the tethered electronic components.